Variable delivery pilot pump control system



W. R. TUCKER Nov. 24; 1942.

VARIABLE DELIVERY PILOT PUMP CONTROL SYSTEM Filed Jan. 4, 1940 5 Sheets-Sheet l Jmwdnv BY WARREN R.TucKER,

. Nov. 24, 1942. w. R. TUCKER 2,302,922

VARIABLE DELIVERY PILOT PUMP CONTROL SYSTEM Filed Jan. 4, 1940 5 Sheets-Sheet 2 Warren 1. TzJcker' INVENTOR.

ATTORNEYS" Nov. 24, 1942. w. R. TUCKER 2,302,922

VARIABLE DELIVERY PILOT PUMP CONTROL SYSTEM Filed Jan. 4, 1940 5 Sh ets-Sheet,v 5

A R Q m w urrlunlllllew Z4;%1M4 f ATTORNEYS Nov. 24, 1942. w. R. TUCKER VARIABLE DELIVERY PILOT PUMP CONTROL SYSTEM Filed Jan. 4, 1940 5 Sheets-Sheet 4 l-Il l-Ill! ATTORNEYS.

Nov. 24, 1942. R. TUCKER 2,302,922

VARIABLE DELIVERY PILOT PUMP CONTROL SYSTEM Filed Jan. 4, 1940 5 Sheets-Sheet 5 Iuv ENTOR WARREN R Tucxuz ATTORNEYS Patented Nov. 24, 1942 VARIABLE DELIVERY PILOT PUMP CONTROL SYSTEM Warren R. Tucker, Dayton, Ohio, assignor to The Hydraulic Development Corp. -Inc., Wilmington, Del., a corporation of Delaware Application January 4, 1940, Serial No. 312,392

15 Claims. (01. 103-38) a This invention relates to a hydraulic system and more particularly to a hydraulic system wherein the servomotor or servomotors of a main variable delivery pump, the output of which is employed to motivate a main hydraulic motor, is controlled by a variable delivery pilot pump. Heretofore, hydraulic systems of this type employing a servomotor have utilized pilot pressure supplied by a small constant delivery pump which is unloaded through a relief or unloading valve after the shifting of the shift ring of the main pump has been accomplished by the servomotor.

The principal object of the present invention is to eliminate all bypassing of hydraulic medium supplied by the pilot pump and also to give a variable speed of shifting the main pump; primarily this object is accomplished by using a small variable delivery pilot pump for actuating the servomotor of the main pump; as a result, the servomotor of the main pump is varied or shiftedby varying or reversing the output of the pilot pump, and after shifting of the servomotor of the main pump has been effected, the pilot pump is shifted to neutral whereby the necessity for using a relief or unloading valve is eliminated.

It is another object to eliminate the power loss and heating of the hydraulic medium attendant upon the use of a relief or unloading valve by eliminating the necessity for using such a valve and providing for shifting of the pilot pump to neutral.

Another object is to provide a closed circuit pilot system by utilizing a reversible delivery pilot pump.

Another object is to provide electrical means for directly controlling the delivery of the pilot pump whereby the pilot pump is automatically so controlled that the main hydraulic motor is actuated in the desired manner.

Another object is to provide means for automatically centering the shift ring of the main allow the main pump to self-center after the' pilot pump has been shifted to neutral by some outside means.

Still other objects will more fully appear.

hereinafter In the accompanying drawings: Fig. 1 is a diagrammatic view of the complete hydraulic and electrical circuit of a hydraulic ,system wherein a solenoid-operated pilot pump delivers variable pilot pressure to actuate the servomotor of the main hydraulic pump and to thereby shift the shift ring thereof and control the direction of delivery thereof.

Fig. 2 is a diagrammatic view showing another mode in which the principles of the present invention may be applied, the reversible variable delivery pilot pump supplying its pressure to the servomotors of the main pump and being controlled by suitable mechanical and electrical mechanism.

' Fig. 3 is a diagrammatic view along the lines of Fig. 2 but showing a modification therefrom in that the pilot pump is manually controlled.

Fig. 4 is a diagrammatic view of still another modification wherein a one-way variable delivery pilot pump actuates a two-way variable delivery main pump.

Fig. 5 is a transverse section on the line 5-5 of Fig. 6 of a one-way variable delivery pilot pump such as is utilized in Fig. 4; with proper modification of the stop means, this pump can be converted to a reversible variable delivery pump and in such case would be applicable to the circuits shown in Figs. 1 to 3.

Fig. 6 is a longitudinal section of the pump of Fig. 5.

Fig. '7 is a transverse section of the pump of Fig. 5 taken on the line 1-1 of Fig. 6, looking' in the direction of the arrows.

Fig. 8 is a diagrammatic view of a still further modification, which may be termed a modification of Fig. 2 in that the shuttle valve of the pilot pump circuit of Fig. 2 has been eliminated and use is made of the fact that the main pump does not shift to neutral when the pilot pump is positively moved to neutral by the return of the platen; another difierence is that provision for self-shifting the main pump towards neutral in response to working pressure so that that pressure can be held indefinitely.

. Fig. 9 is a similar view of a still further modification wherein the shuttle valve of the pilot pump circuit is eliminated and a platen-actuated two-way valve is substituted; in this modification the pilot pump is held on stroke continuously and is never positively moved to neutral.

General arrangement In general, the present invention contemplates the application of a variable delivery pilot pump in place of the constant delivery pilot pump heretofore employed for control of the output of a main pump which is used in any desired manner, as for example for actuating the ram of a press-. ing hydraulic motor. In a preferred form, a reversible variable delivery pilot pump is employed for this type of service. The pilot pump is adapted to have its output controlled either me chanically as by some outside means such as the motion of the pressing platen or manually operated shifting means, or hydraulically by the attainment of a predetermined pressure in the output of the pilot pump after the shifting of the main pump has been accomplished. Desirably, means is provided for automatically short-circuiting the output of the pilot pump so as to allow the main pump to automatically shift to neutral when the pilot pump has been shifted positively to neutral, this being accomplished by the provision of a special type of shuttle valve in the output of the pilot pump. It is also desirable to provide for automatically self-centering the shift ring of the main pump when the pilot pump has been shifted to neutral by some outside means. These generalities will be more fully understood as the following description of several hydraulic circuits embodying the principles of the present invention proceeds.

Embodiment of Figure 1 The pilot pump I is of the reversible variable delivery type. This pump has a shift ring 2 which is adapted to reverse or vary the delivery thereof. A solenoid 3 is provided for shifting the shift ring to the left and a solenoid 4 is likewise provided on the opposite side of the pump for shifting the shift ring to the right, this shifting being accomplished by the shift rods 5 and 5 which are fixedly carried in any suitable manner by the armatures of the solenoids 3 and 4. A compression spring |2 associated with the shift rod 5 is compressed when solenoid 4 moves the shift ring to the right and a corresponding spring I3 associated with shift rod 9 is compressed when the solenoid 3 moves the shift ring 2 to the left. Springs I2 and I3 move the shift ring 2 into the central or neutral position whenever the solenoids 3 and 4 are deenergized.

The main tank 1 is connected by a line 8 to the shuttle valve 9 which is of a special type, the shuttle valve 9 being connected by the line I!) to the upper inlet or outlet of the pilot pump I, and by a line H to the bottom inlet or outlet of the pump I. A line l4 connects the line ID to a main pump servomotor l6 while a line |5 connects the line H to the other side of the servomotor Hi. The servomotor I6 is adapted to shift the shift ring l8 of the main pump I! by means of piston 20 which is connected to the shift ring |9 through shift rod I9 which is integral with piston 20 and which is threadedly received in one side of shift ring IS. A pair of oppositely disposed compression springs 2| and 22 are mounted within the cylinder of the servomotor l5 and act on opposite sides of the servomotor piston 20 to center the shift ring l8 whenever the pressures in lines l4 and I5 are equal and atmospheric.

The shuttle valve 9 comprises a cylindrical casing divided into three compartments which compartments are connected respectively to lines ment is connected to the inlet line 8 while the end I!) and II leadin to the pilot pump I. A valve member 25 having spaced valving heads within the end compartments is adapted to be moved by pressure in an end compartment so as to shut off the end compartment and simultaneously place the other end compartment into free communication with the central compartment. The shuttle valve 9 is generally of the construction shown as elements IE to 2| in Ernst Patent No. 1,653,350, but has in addition the centrally located shoulder 26 which is adapted to be engaged by compression springs 21 and 2B and to thus move the valve member 25 normally to the middle whereby free communication is established between conduits l0 and II for a purpose which will hereinafter appear.

One side of the main pump I! is connected by a line 29 to the bottom of a hydraulic cylinder 3| while the other side of pump I1 is connected by a line 3|] to the top of cylinder 3|. Operating within cylinder 3| is th main hydraulic piston 32 connected by the piston rod 33 to the press platen 34. The pump I1 is adapted to be supplied with liquid from tank I to make up for any leakage occurring in its circuit or to compensate for the differences in effective area between the top and bottom of piston 32 by a line 35 which connects tank I to a shuttle valve 36, shuttle valve 35 being connected by line 31 to the line 30 and by line 38 to the line 29.

The electrical circuit of Fig. l is as follows:

The incoming power lines are designated 39 and 40. A manually operable switch 42 is adapted to establish a circuit through a solenoid 4| which causes the armature of solenoid 4| to establish a circuit through to the solenoid 3 and back to the power line 39 by a line 44, at the same time establishing a holding circuit for the armature 43 through tonnag switch 46 to the line 44. The tonnage switch 46 is normally in the position shown but when a predetermined pressure arises in conduit 30 towards the end of the pressing operation, this pressure is conveyed through a conduit 41 to the tonnage hydraulic motor 48 operating the tonnage switch 46 so as to break the holding circuit thus established and simultaneously make a circuit between line 44 and a line 49 across the coil of a solenoid 50, through a line 5|, a limit switch 52 which is closed except when the platen 34 is in its uppermost position and a line 53 back to the power line 40 and at the same time establish a holding circuit by means of the lower blade carried by the armature 54 of the solenoid 50. Simultaneously, the upper blade of armature 54 of solenoid 50 establishes a circuit from line 44 through the solenoid 4 back to the line 40 by way of line 53.

An emergency switch 55 is provided in line 44 for breaking any circuit which may be established either through solenoid 4| or 50 for thereby allowing pump to be shifted to neutral by the springs l2 and I3 for thereby allowing pump IT to be shifted to neutral by the springs 2| and 22 for thereby stopping the platen 34 in its movement, regardless of in which direction this movement may be.

Operation 0 f the system of Figure 1 With the mechanism as shown in Fig. 1, in order to cause the platen 34 to lower, the operator manually closes switch 42, causing the armature 43 of the solenoid 4| to lower and to establish a holding circuit through the lower switch blade of the tonnage switch 45 and to energize solenoid 3, causing the pilot pump shift rod 5 to be moved leftwardly against the action of the spring I3.

Thereupon, the pilot pump I is placed on stroke in a direction such as to draw liquid from conduit I and to supply liquid under pressure to conduit I4, causing the shift ring I8 of th main pump to be shifted leftwardly, causing the main pump I1 to deliver liquid under pressure through conduit 30 to the space above the main pressing piston 32 and to withdraw liquid through conduit 29 from the space below piston 82. As piston 32 is thus lowered, the additional liquid required by pump I1 i withdrawn from the tank 1 by means of the operation of shuttle valve 36. Im-. mediately when the platen 34 begins to lower, the limit switch 52 is closed, placing the circuit in condition for the energizing of solenoid 50.

When pilot pump I has delivered suflicient liquid under pressure to effect the shifting of the ring I8 of pump I1, the shifting piston 20 will have moved by the port of the return conduit I5. Continued operation of pilot pump I will cause the piston 20 to hold this position. Should piston 20 slip rightwardly so as to seal the port of conduit I5, the liquid pressure supplied by conduit I4 would immediately cause piston 20 to move leftwardly, thus holding the pump I1 on stroke in a direction to deliver into conduit 36.

When the platen has effected the pressing operation, the pressure in conduit 38 will increase to such an extent that the pressure transmitted to tonnage motor 48 will be suflicient to overcome the force of its spring and to force the switchcarrying member 46 upwardly, thereby breaking the circuit through solenoid 4| and thereby deenergizing the solenoid 3. At the sam time, the upper switch blade of member 46 will establish a circuit through solenoid 50 which will establish a holding circuit by the lower blade of armature 54 and-a circuit through solenoid 4 by its upper blade. This energization of solenoid '4 will cause the rod 6 to move the shift ring 2 of the pilot pump past the neutral position onto stroke in the opposite direction, spring I2 being compressed as this occurs. This will cause pilot pump I to deliver liquid under pressure into conduit l5 and to withdraw liquid from conduit I4. As the pump I passed through the neutral position, the pressure in line I4 was reduced to atmospheric and this caused the shift piston 20 to move rightwardly of the port of conduit I 5. Thus, as liquid under pressure is supplied to conduit I5 it forces shift piston 29 rightwardly of the port of conduit I4 and causes main pump I1 to be placed on stroke in the opposite direction; delivering liquid under pressure to conduit 29 and withdrawing liquid from the space above piston 32 through conduit 36. Th excess liquid squeezed out of the space above piston 32 is returned to the tank 1 by the shuttle valve 36. Th operation of shuttle valve 36 will be obvious to those skilled in the art, particularly in the light of the Ernst Patent 1,653,350 referred to above.

Under the influence of the pressur liquid in conduit 29, the platen 34 will thus rise until it engages the limit switch 52, causing the circuit established thereby through solenoid 50 to be broken and simultaneously causing the circuit through solenoid 4 to be broken. This causes the shift ring 2 of the pilot pump I to be returned to neutral by the action of the centering springs I2 and I3. The apparatus is now in condition for the repetition of another cycle by the momentary manual closing of the start switch 42. Should it be desired at any time to stop the motion of the platen 34, the operator will manually open the emergency stop switch 55, thus breaking the circult through solenoid 4I or 50 and shifting the pilot pump to neutral.

Relief is allowed in conduits I4 and I5 for shifting of the piston 20 to neutral by means of the modified shuttle valve 9 whose operation is as follows. The establishment of liquid under pressure in conduit II causes the valve member 25 thereof to move rightwardly, compressing spring 28 and allowing free communication between conduits 8 and I0. Similarly, the building up of liquid pressure in conduit I0 causes the valve member 25 to move leftwardly, compressing spring 21 and allowing free communication between conduits II and 8, thereby likewise allowing the pump I to withdraw from tank 1 any additional liquid required to make up for leakage or because of the difference in effective areas of the two sides of the servomotor piston 20. Immediately upon the shifting of the pilot pump I to neutral, the pressure in theconduit I0 or II which was under pressure is lowered to that exerted by the spring 2I or 22 which was under compression. The centering springs 21 and 28 of the shuttle valve 9 move the valve member 25 to the medial position, thereby allowing free communication between conduits l0 and II and allowing relief of the servomotor piston 28 so that it is free to center the shift ring I8 of the main pump I1 under the influence of centering springs 2I and 22.

It will be understood that springs 21 and 28 may be very small and still effective to center the valve member 25 against the pressure in conduit III or II exerted by ,the main pump spring 2I or 22, respectively, through the piston 28, the elfective areas of the piston heads of the valve member 25 being also proportioned to the effective area of shifting piston 20 to effect this result.

The shuttle valve 9 is designed to restrict the passage of fluid at the two ends thereof sufficiently so that when the pilot pump moves to full stroke in either direction, back pressure will build up in the pilot system to actuate the main pump servomotor.

From the foregoing, it will be seen that novel and highly effective means is provided for the control of the main pump l1 and that this means comprises double-acting means for shifting the ring of the pilot pump I and a double-acting servomotor I6, these elements cooperating in a novel manner with the other elements in the system to produce a new and more effective hydraulic control.

Modification shown in Figure 2 In this figure, the pilot pump 56 has the shift ring 51 which is engaged by the shift rods 58 and 59, the shift rod 58 being connected by the bell crank 60 and the link 6I to a rocker arm 62, one end of which is adapted to be moved upwardly by a rod 63 upon which is adjustably fixed a collar 64 adapted to be engaged by a yoke 65 secured to the platen 66. Rocker arm 62 is adapted to be rocked by the platen 66 reaching its upward stroke in such direction as to shift-the shift ring 51 rightwardly, thereby compressing the spring 61 in the cylinder 68 attached to the side of the pilot pump 56. The shift rod 59 carries a piston 69 which is adapted to compress the spring 61 and to be moved hydraulically as will presently appear. Similarly, the shift rod 58 carries a piston 10 operating within a hydraulic cylinder H in a manner which will presently appear. A spring 12 is interposed between halves of the link 6|, this spring 12 being strong enough to overcome the spring 61 at the right of the pilot pump.

The collar 64 is so adjusted as to move the' shift ring 51 of the pilot pump only to neutral when the platen 66 reaches its upper position. In order to shift the pump onto stroke in this same direction, a solenoid 13 is operatively connected to the rocker arm 62 and when the solenoid 13 is energized, it shifts the shift ring of the pilot pump against the action of spring 61 onto stroke in a direction such that the pump delivers into conduit 14 and sucks liquid from conduit 15. A conduit 16 connects conduit 14 to the cylinder 68 in such manner that when the pressure builds up in conduit 14, it is eifective in conjunction with spring 61 to force the piston 69 leftwardly, thereby shifting the pump 56 towards neutral, this motion being taken up by the spring 12, whereby the armature of solenoid 13 and rocker arm 62 retain their position.

Similarly, a conduit 11 leads from the conduit to the cylinder 1| so that when the pump is on stroke in the opposite direction, the pressure built up in conduit 15 after shifting of the main pump has been effected is transmitted to cylinder 1| and causes the piston 18 therein to shift the pump towards neutral from the other direction.

Spring 61 is of such strength as to normally move the shift ring 51 of the pilot pump 56 leftwardly so as to place the pilot pump on stroke in a direction such that it delivers into conduit 15.

Conduits 14 and 15 are connected respectively to servomotor cylinders 18 and 19 of a main pump 80.' Hydraulic servomotor pistons 8| and 82 respectively are disposed in cylinders 18 and 19 and are adapted to move the shift ring 83 of the main pump. A pair of springs 84 and 85 normally tend to move the pistons 8| and 82 respectively inwardly towards the main pump, thereby effecting automatically 2. self-centering action, these springs being of equal strength.

The main pump 88 is adapted to deliver pressure liquid either to a conduit 86 and thence to the top of main piston 81 which actuates the platen 66 or to a conduit 88 to the bottom of piston 81, depending upon the position of its shift ring 83.

Conduit 15 is adapted to be placed into communication with the tank 89 by a conduit 98 leading to a modified shuttle valve 9|, while conduit 14 is likewise adapted to be placed into communication with tank 89 by a conduit 92 leading to the other end of the shuttle valve 9|. Shuttle valve 9| is constructed as is shuttle valve 9 in Fig. 1 and has its central chamber in com-. munication with the tank 89 at all times by means of a conduit 93.

A shuttle valve 88a of conventional type has its central chamber connected to tank 89 by line 88b and its endchambers connected to the main pump lines 86 and 88 by conduits 88c and 88d, respectively.

Operation of system of Figure 2 With the parts in the position shown, if it is desired to eifect downward movement of platen 66, the operator energizes solenoid 13, thus causing the shift ring 51 of pilot pump 56 to move rightwardly, causing liquid pressure to be built leftwardly, causing liquid pressure to be built up in conduit 86 and to be thence transmitted to the upper side of the main piston 81. As soon as the piston 82 has moved leftwardly to effect this shifting from the neutral position, liquid pressure built up in conduit 14 will act through conduit 16 to move the piston 69 of the pilot pump leftwardly, causing compression of spring 12. This will shift the pilot pump 56 towards neutral. However, it will not entirely reach neutral because there is always some leakage in the system and the pump 56 is therefore always slightly on stroke. This stroking maintains sufficient pressure to keep the valve member in shuttle valve 9| shifted leftwardly, whereby communication between conduits 14 and 15 is prevented.

When the platen 66 reaches its downward position, suitable means is operated for de-energizing the solenoid 13 whereupon the spring 61 forces the shift ring 51 of the pilot pump 56 all of the way to the left, thereby putting the pump 56 on stroke in the opposite direction. This causes liquid under pressure to be delivered into conduit 15 and causes liquid to be withdrawn from the conduit 14. This causes the servomotor piston 82 to move rightwardly, moving the shift ring 83 of the main pump and causing the main pump to deliver liquid under pressure into conduit 88, causing the platen 66 to move upwardly. As soon as the piston 82 has moved rightwardly as far as possible, pressure is built up in conduit 15 which is transmitted through conduit 11 to the left-hand of piston 10, causing piston 18 to shift the shift ring 51 of the pilot pump 56 towards neutral. Again the shift ring will not completely reach neutral because of slight leakage in the system whereby the pump is always slightly on stroke and again maintains sufficient pressure in conduit 15 to hold the valve member of shuttle valve 9| rightwardly, thereby preventing communication between conduits 14 and 15.

As the platen 66 reaches its uppermost position, its yoke 65 engages the collar 68 and causes the shift ring 51 of the pilot pump 56 to be positively moved to the exactly central or neutral position. Immediately when the pilot" pump is shifted to neutral by this outside means, the pressure in the outlet side 15 drops to that exerted in line 15 by the servomotor spring 84 which is now compressed. There is always some slight leakage and the smallest leakage is sufficient to immediately lower the pressure in the outlet conduit 15 to this figure. The spring of shuttle valve 9| now moves the shuttle valve member to'the central position, allowing a free communication between conduits 14 and 15, thus allowing the springs 84 and 85 to center the shift ring 83 of the main pump 88 and thus to position and maintain the main pump accurately in neutral, whereby falling of the platen 66 is prevented since the pump is prevented from acting as a motor. Due to the great difference in areas between the piston 82 and the left-hand piston of the shuttle valve 8|, a much smaller spring in the shuttle valve is enabled to shift the shuttle valve member against the pressure in line 15 exerted by the spring 84.

Modification of Figure 3 In Figure 3, there is shown a modified form which differs from Figure 2 only in that the control of the pilot pump 56 is changed so as to be manual by the elimination of the means for electrically shifting the pilot pump and the means for shifting the pilot pump to neutral when the platen 95 has returned to its uppermost position.

, Instead, the pilot pump 59 is shifted manually by means of a, pivoted manually operated lever 94 which operates bymeans of springs 95 and 99 piston 99 will be moved rightwardly. Similarly,v

a conduit I02connects the conduit 14 to the other side of piston 99 so that when pressure is built up in conduit 14 the piston 99 will be moved leftwardly.

In operation, the operator first moves manual lever 94 to the desired position leftwardly, thus causing the shift ring 51 to be moved rightwardly and causing the application of liquid under pressure to the right hand servomotor of the main pump 80, this causing a delivery of liquid to the top of the main piston 91. After the shifting operation, the building up of liquid pressure in conduit 14 moves piston 99 leftwardly against the action of spring 96, thereby moving the shift ring 5? towards neutral. After the pressing operation, the operator moves the lever 94 inthe op- I posite direction, whereupon the shift ring 51 is shifted leftwardly, whereupon liquid under pressure is delivered to the left-hand servomotor of main pump 90, whereupon main pump 90 is shifted so as to deliver liquid under pressure to conduit 90, thereby effecting return of the pressing piston 81. As soon as the servomotor shifting has been accomplished, the building up of liquid pressure in conduit 15 causes piston 99 to move rightwardly against the action of spring 95, thereby causing the pump to be shifted towards neutral; When the return of the piston 91 has been accomplished, the operator will move the lever 94 to the neutral position, whereupon the shift ring 51 is moved to neutral and the shuttle valve 9i operates so as to establish fluidcommunication between conduits 14 and 15 and to allow the shift ring 93 of main pump 80 to be centered under the action of the centering springs 94 and 85.-

By setting the lever 94 at the desired position, a variation in the speed of shifting the mam pump 80 can be effected.

Modification shown in Figure 4 In Fig. 4, there is illustrated the application of the principles of the present invention to a situation where a one-way variable delivery pump is utilized. The pilot pump H is adapted to withdraw liquid from tank III by means of the conduit H2 and to deliver liquid into the conduit H3 which leads to the servomotor control of a main pump H4. The main pump H4 is adapted to deliver liquid under pressure either to a conduit H5 and thence to the top of a main hydraulic motor H5 or to a conduit H1 and thence to the bottom of hydraulic motor H6. As before, a shuttle valve H9 of the conventlonal type is provided between the tank III and conduits H5 and H1.

is more fully indicated in Fig. 5, the pilot H0 has a shift ring H9 which is adapted to be moved normally to the right to full stroke by a spring I20 which pushes against a shift member I2I engaging the spring I20 is adapted to have its force varied by the adjusting screw I22.

shift ring H9. The

In order to-shift the pump I I0 to neutral, the shift ring H9 is moved leftwardly of Fig. 5 until its shift ring H9 engages the boss I23 at the left which surrounds the member I2I and which v is adapted to act as a st'opfor shift ring H9 in the neutralposition. The shift member I24 is adapted to be moved leftwardly y the stepped hydraulic piston I25. In order to actuate piston I25, a series of ports I29 and I21 corresponding in number to the number of steps is provided, only the desired port being used. As shown, the pressure built up in conduit II 9 is adapted to be transmitted after a shifting of the pump H4 by means of a conduit I29 to the port I26 and to thereby act upon the large diameter annular portion of piston I25. If it is desired to actuate the ring I I9 at a higher line pressure, the plug in port I21 may be removed and conduit I29 led into port I21. If it is desired to actuate shift may be branched and led into both ports I26 and I21.

The servomotor control for main pump H4 indicated at the left thereof is shown specifically in the copending application of Walter Ernst, Serial No. 170,250, filed October 21, 1937,

which has matured to Patent No. 2,184,665. This servomotor control, therefore, does not per se constitute any part of the present invention.

As shown, the servomotor control comprises a stepped servomotor cylinder I29 in which is slidably mounted a stepped piston I30 which is fixedly connected at its rightward end to the shift ring I3I as by means of threading thereinto. Fixedly carried by the piston I3 is a sleeve I32 which is adapted to slidably engage a valving member I33 in the form-of an enlarged cylindrical portion of a servomotor control rod I34.

A spring I35 normally urges the rod I34 outwardly and rod I34 is adapted to be reciprocated by the lever I39. The pressure inlet H3 connects move the piston I30 inwardly, thereby shifting shift ring I3I until the valve member I33 seals the left-hand ports in sleeve I32. This causes pump H4 to deliver liquid either to conduit H5 or to conduit H1. When it is desired to shift the ring I3I in the opposite direction, the lever I36 is oppositely actuated, moving the control.

rod I34 leftwardly, sealing the left-hand ports in the sleeve I32 and causing pressure liquid to be applied to the largest stepped portion of pis-' ton I30 directly from the annular zone I31. As the piston I30 moves leftwardly in response to this pressure, the liquid from zone I40 is discharged through axial ports shown in dotted lines to the rightward radial ports to sleeve I32, thence into the chamber accommodating spring I35, thence outwardly through inclined ports MI in the piston I30, thence to the annular zone I39 to the return conduit I39. This leftward motion of piston I30 continues until it has caused the rightward ports of sleeve I32 to be sealed by -75 their engagement with the valve member I33.

ring H9 at a lower line pressure, conduit I29 The conduit I42 is provided solely to take care of leakage along the rod I34.

In order to effect operation of the mechanism shown in Fig. 4, the pump H is continuously operated and shifting of shift-ring I3I is effected by manual or automatic operation of lever I36 so as to cause the servomotor piston I30 to move either to the right or to the left. Immediately upon the shift ring I3I attaining its position to the right or to the left, pressure will be built up in conduit H3 and will be transmitted through conduit I28 to act upon the piston I25 of the pilot pump H0 and to shift the ring II8 thereof towards neutral. Should any leakage occur in the servomotor control, the pressure in conduit I28 will diminish and pilot pump IIO will be immediately placed on stroke to the necessary extent under the action of spring I20.

After a pressing in one direction has been efiected, lever I36 will be operated in the reverse direction, whereupon hydraulic motor II6 will be operated so as to retract its ram.

Pilot pump construction As indicated in Figs. to '7, the pilot pump IIO comprises a housing I43 which is provided with passageways I44 and I45 of which passageway I44 is the inlet passageway connected to conduit I I2 and passageway I45 is the outlet passageway connected to conduit I I3. The pump comprises a rotor I46 integral with a shaft [41 which is journaled in the housing by means of bearings I48 and I49. Fixedly mounted on the shaft I41 is a distributing sleeve I50 which has an integral flange I5I forming the left side wall of the rotor.

A side wall I52 is fixedly mounted as by shrinking on the other side of rotor I46. Slidably mounted in the rotor I46 are vanes I53 which are adapted to carry with them a rotatable cylindrical ring I54 which functions as the inner race of a ball bearing which comprises the balls I55 and the outer race II8 which functions as the shift ring of the pump. The rotor is provided with the ports I56 which extend inwardly from working chambers thus formed and thence to the side of the rotor. Distributing sleeve I50 is likewise provided with ports I51 which extend axially from communication with the ports I56 and thence radially outwardly. In order to valve the working chambers of the pumpand to separate the pressure side of the pump from the suction side, the annular collecting space I58 is provided at the top of the sleeve I50 in the housing I43 and a similar annular collecting zone I58 is provided at the bottom, these zones being separated by the curved protuberances I60 and lil which are of a peripheral length greater than the width of ports I51. 7

Thus, as the rotor I46 is rotated, thevanes I53 carry the ring I54 with them and valving and porting of the chambers is accomplished-by the collecting zones I58 and I59 and the division portions I60 and I6I. It will be seen that, assuming clockwise rotation of the rotor in Fig. 5, the upper working chambers become suction chambers and suck liquid from inlet I44 while the lower chambers become pressure chambers and force the liquid under pressure into passageway I45. It will further be seen that by shifting the shift ring II9 transversely, the eccentricity of the ring I54 relative to the rotor I46 may be varied and that the delivery of the pump may thus be varied. When the ring I54 is concentric with the rotor I46, the pump is in neutral and no delivery is made. This happens when the ring H9 is in engagement with the boss I23 which acts as a stop for the ring.

Modification of Figure 8 In Fig. 8, there is portrayed diagrammatically a modification of the arrangement of Fig. 2. The pilot pump shuttle valve has been eliminated and conduits I4 and I5 are connected by conduits 88a. and 88b to a conduit 890 which leads to the tank 89. Check valves 89d and 88a are disposed in conduits 88a and 8%, these check valves being adapted to allow liquid to be sucked from tank 88 into conduit I4 or I5 for make-up purposes to compensate for leakage, but to prevent the reverse flow. A further difference from the construction of Fig. 2 resides in the provision of a conduit 86a leading from the upper outlet conduit 86 of pump to the right-hand servomotor cylinder I8 at a point leftwardly of the piston 8|.

, causes the platen 66 to travel slightly beyond the position required to shift the pilot pump 66 to neutral. This overtravel of platen 66 is trans .mitted through the rocker arm 62, the link 6|,

the spring I2, and the bell crank 60 to the shift rod 58, causing the pilot pump 56 to be shifted slightly on stroke in a direction such as to deliver liquid into conduit I4, thereby causing the main pump 80 to be shifted to neutral. In fact, the main pump 80 will be shifted somewhat past neutral causing liquid to be delivered into conduit 86 and causing the platen '66 to move downward slightly, this causing the pilot pump 56 to be shifted slightly on stroke in a direction such as to deliver liquid into conduit I5, causing main pump 80 to be again shifted slightly onto stroke in a direction such as to deliver liquid into conduit 88, thereby causing the platen 66 to again move upwardly slightly. Thus, in this arrangement, the platen 6 6 will hunt back and forth for a short period of time until main pump 80 and pilot pump 56 are both in neutral. Should the platen 66 drop slightly due to leakage, it will cause the pilot pump 56 to be placed on stroke in such direction as to deliver liquid into conduit I5, thereby causing the main pump 80 to be shifted slightly onto stroke so as to deliver liquid into conduit 88, thereby causing the platen 66 to be elevated again.

The provision of conduit 86a causes the main pump to shift itself towards neutral in response to the development of working pressure in the conduit 86, this working pressure being transmitted through conduit 86a so as to shift the shift ring of the main pump 80 rightwardly and towards neutral. As the pressure is built up on the left-hand side of piston 8|, it moves piston 8| rightwardly, thereby forcing the liquid on the right-hand of piston 8| into conduit 14 and thence through conduit I6 into the chamber at the right-hand of control piston 69 of the pilot pump. The pilot pump was already almost at neutral and this application of pressure will cause piston 69 to shift pump 56 to neutral and then onto stroke in the other direction so as to suck liquid from conduit 14 and deliver the main pump 80 to neutral.

conduit and thence effectively against servo- 83 will be shifted to just that point where pump 80 is operative to maintain the working pressure in conduit 86, and will not go any further than this because any drop in pressure in line 86 below the working pressure attendant upon such further travel of shift ring 83 too far towards neutral would cause piston 8| to be moved leftwardly which would allow compressed spring 12 to shift pilot pump 56 onto stroke so as to deliver liquid under pressure into conduit 14. Thus main pump ,88 will deliver into conduit 86 indefinitely liquid under the working pressure so that the working pressure may be held indefinitely on the material or article being pressed.

Modification of Figure 9 In Fig. 9, the construction is generally similar to that of Fig. 8 but the provision for self-shifting of the main pump towards neutral in the form of conduit 86a has been eliminated and the control of the pilot pump is modified. The pilot pump is adapted to have its shift ring 51 shifted by a shift rod I62 which has an integral piston I63 slidably operating in a control cylinder I64, a spring I65 bearing against the piston I63 and normally urging the shift ring 51 rightwardly so as to place the pump on stroke in such direction as to normally deliver liquid into conduit 15 whence it passes to the left-hand servo-motor cylinder 19 of the main pump 80 and is adapted to move the shift ring 83 thereof rightwardly so as to move the platen 66 upwardly. A solenoid I66 has its armature connected to a rod I61. A spring I68 is provided between a housing I69 therefor fixedly carriedby shift rod I62 and a collar integral with the end of rod I61. When the solenoid I66 is energized, it pulls the rod I61 leftwardly and thereby through the spring I68, pulls the shift rod I62 leftwardly and the shift ring 51 leftwardly so as to place the pilot pump 56 on stroke in the opposite direction in which it delivers liquid into conduit 14 whence the liquid under pressure passes to the rightward servomotor cylinder 18 and causes main pump 80 to be placed on stroke in such direction as to deliver liquid under pressure into conduit 86, thereby causing platen 66 to move downwardly for a pressing operation. As the parts are shown, the solenoid I66 is de-energized and the pump 56 is delivering liquid into conduit 15, thence through a check valve I10, line I1I, thence through a then open two-way valve I12 which is held open by the cam I13 carried by the platen 66 against the action of a spring I14, and thence by way of a conduit I15 to conduit 14 and back to the pump 56. When the solenoid I66 is energized so as to shift the pump 56 onto stroke in the other direction so as to cause a pressing operation, the

liquid from conduit 14 is prevented from traveling in a reverse circuit by the check valve I18 which closes and causes the pressure developed in conduit 14 to be effectively applied to the righthand servomotor piston 8I, thereby causing the main pump 80 to be shifted so as to deliver pressure liquid into conduit 86, thereby causing platen 66 to begin lowering. As soon as the platen 66 starts downwardly, the cam I13 causes the valve I12 to be closed under the thrust of spring I14 preparatory to a reversal operation. Since valve I12 is closed when the platen 66 reaches the limit of its downward travel and it is desired to cause it to move upwardly, when the solenoid I66 is de-energized for a retraction stroke of platen 66, the shift ring 51 assumes the position shown in Fig. 9 and pump 56 deliver's liquid into motor piston 82, thereby shifting main pump so as to cause it to deliver liquid under pressure into conduit 88, thereby causing platen 66 to lift.

When platen 86 reaches its uppermost position, cam I13 causes valve I12 to be opened, thereby allowing the liquid under pressure at the lefthand of servomotor piston 82 to pass outwardly through check valve I10, line I1I, open valve I12, line I15, and conduit 14 to the right-hand of servomotor piston 8I, thus equalizing the pressures on pistons 8I and 82 and thus allowing the springs 84 and 85 to move the shift ring 83 of the main pump 80 to neutral.

With the platen thus elevated and the main pump 80 in neutral, should platen 68 drop for any cause, as for example due to leakage below piston 81, its cam I13 will cause valve I12 to partially close under the influence of spring I14, causing a restriction and causing the liquid being supplied into conduit 15 to begin to be applied against servomotor piston 82 so as to cause slight shifting of main pump 80 in a direction such as to place pump 80 on stroke, delivering liquid into conduit 88 and causing elevation of platen 66.

As before, means is provided for shifting the pilot pump 56 towards neutral from delivery in either direction after it has caused shifting of the main pump onto stroke in either direction. This means as before, takes the form of conduit I16 transmitting the liquid pressure from conduit 15 to the right hand of piston I63 and conduit I11 transmitting the liquid pressure in conduit 14 to the left-hand of piston I63. These control conduits I16 and I11 function as follows:

Assuming that a pressing operation is being initiated, solenoid I66 is energized, causing the shift ring 51 to be moved leftwardly against the action of spring I65 and causing liquid pressure to be built up in conduit 14, causing main pump 88 to be shifted so as to deliver in conduit 86. When main pump 88 has been shifted by this liquid pressure, liquid pressure in conduit 14 builds up very rapidly and is transmitted through conduit I11 to the left-hand of piston I63, therebyshifting the ring 51 of the pilot pump rightwardly towards neutral against the action of spring I69. Similarly, at the bottom of the stroke of platen 66 when it is desired to lift platen 66, solenoid I66 is de-energized, causing the shift ring 51 to move rightwardly under the influence of spring I65 and causing liquid under pressure to be built up in conduit 15 and applied so as to shift the ring 83 of main pump 80 rightwardly so as to deliver liquid into conduit 88. After this shifting ha's'been accomplished, the still further buildup of liquid pressure in conduit 15 is transmitted through conduit I16 to the right-hand of control piston I63, thereby shifting the ring 51 of the pilot pump leftwardly towards neutral in opposition to the spring I65.

Provision is desirably made for adjusting the upward or idling point of the press,,by providing for the vertical positioning or adjustment of the cam I13 in any desired manner. This is possible because cam I13 causes opening of valve I12 and thus causes the press to stop at the point where it effects this opening of valve I12. In this way, adjustment is provided for differing conditions of operation.

From the foregoing description, it will be seen that the present invention provides for simplification and increased operating efficiency of hydraulic circuits which have hitherto employed a constant delivery pilot pump. These results are brought about in large measure by the use of a variable delivery pilot pump. In addition to the advantages referred to in detail above, numerous other advantages of the present invention will immediately be apparent to those skilled in the art and it is not deemed necessary to detail them at length here.

It will further be seen that the use of a variable reversible flow pilot pump makes possible considarable simplification of the press control system. The main radial pump control may be, as illustrated, a simple double-acting hydraulic piston without the complicated servomotor control shown for the main pump in Fig. 4. The invention permits a simplified control for the variable reversible delivery pilot pump. Due to the fact that the forces involved in shifting the pilot pump are relatively small, the linkage for reversing the pilot pump may be connected mechanically directly to the pilot pump shifting ring without an intervening hydraulic servomotor control. In addition, as illustrated, means such as a relatively simple spring and plunger arrangement may be provided for regulating the pilot pressure by utilizing the variable stroke feature of the pilot pump.

I wish it to be understood that I intend to include as within the invention such modifications and adaptations thereof as may be necessary to adapt it to varying conditions and uses and as fall within the scope of the appended claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is: v

1. A hydraulic system comprising in combination a hydraulic plunger, a reversible variable delivery main pump to supply pressure fluid to said plunger to actuate the same, double-acting servomotor means associated with said main pump for varying and reversing the delivery thereof, a reversible variable delivery pilot pump, for supplying pressure fluid to said servomotor means to actuate the latter, means responsive to the pressure condition in said servomotor means for reducing the delivery of said pilot pump without affecting the delivery of said main pump,

yielding means continuously urging said main pump to neutral or no delivery position, and means adapted at the end of the retraction stroke of said plunger to make said servomotor means ineffective, thereby allowing said yielding means to move said main pump to neutral position.

2. A hydraulic system comprising a hydraulically reciprocable plunger, a variable delivery main pump for supplying pressure fluid to said plunger to actuate the same, a servomotor means associated with said pump for controlling the delivery thereof, a reversible variable delivery pilot pump, means for connecting the output of said pilot pump to said servomotor means to actuate said servomotor means, servomotor means including a double-acting fluid operable piston for said I pilot pump, means for connecting the outputof said pilot pump selectively to one or the other side of said piston, to move said pilot pump towards neutral delivery position in response to a predetermined pressure in said first-named servomotor means, and means for short circuiting the output of said pilot pump in response to a predetermined point of travel of said plunger, to initiate movement of said main pump to substantially no delivery position.

3. In a hydraulic system, a hydraulic motor,

a variable delivery main pump for supplying pressure fluid to said motor for actuating the same, servomotor means for controlling the delivery of said main pump, a variable delivery pilot pump, means for connecting the output of said pilot pump to said servomotor means, means for shifting said pilot pump to neutral, means operatively connected with said motor for shifting said pilot pump to substantially no-delivery position, and means for automatically shifting said main pump to neutral when said pilot pump is shifted to neutral.

4. In a hydraulic system, a hydraulic motor, a reversible variable delivery main pump for supplying pressure fluid to said motor for actuating the same, servomotor means for controlling the delivery of said main pump, a variable delivery pilot pump, means for hydraulically connecting said pilot pump to said servomotor means, means operatively connected with said motor for shifting said pilot pump to neutral, and means for, automatically shifting said mainpump to neutral when said pilot pump is shifted to neutral comprising self-centering spring means associated with said servomotor means for normally urging said main pump-to neutral and hydraulic means for relieving said servomotor means when said pilot pump is shifted to neutral for thereby allowing said spring means to freely center and shift said main pump to neutral.

5. In a hydraulic system, a hydraulic motor, a reversible variable delivery main pump for supplying pressure fluid to said motor for actuating the same, servomotor means for controlling the delivery of said main pump, a reversible variable delivery pilot pump, means for connecting said pilot pump to said servomotor means to oppositely actuate the same so as to cause said main pump to oppositely deliver, external means for shifting said pilot pump so as to deliver in either direction, spring means for shifting said pilot pump to neutral when said external means is rendered inoperative, and spring means for shifting said main pump to neutral when said pilot pump is shifted to neutral.

6. In a hydraulic system, a hydraulic motor, a reversible variable delivery main pump for supplying pressure fluid to said motor for actuating the same, shift means therefor for controlling the delivery thereof, double-acting servomotor means for controlling said shift means, said servomotor means comprising a reciprocable piston operatively connected to said shift means and a cylinder for said piston, said cylinder having a pair of ports normally disposed on each side of said piston, a reversible variable delivery pilot pump, and a pair of conduits connecting said pilot pump to said ports, whereby the output of said pilot pump is adapted to move said piston and thereby said shift means until said piston uncovers the one of said ports which is connected to the return one of said conduits and to maintain said piston in said position.

7. In a hydraulic system a fluid operable motor, a reversible variable delivery main pump for supplying pressure fluid to said motor for actuating the same, double-acting servomotor means for controlling the delivery of said main pump, a reversible variable delivery pilot pump, doubleacting servomotor means for controlling the delivery thereof, a pair of conduits connecting said pilot pump oppositely to said main servomotor means, a pair of conduits connecting said pilot pump oppositely to said pilot servomotor means, external means adapted to be manually operated for overcoming said pilot servomotor means and additionally controlling the delivery of said pilot pump, and yielding means for allowing said pilot pump to be shifted towards neutral without changing the setting of said external means after said pilot pump has caused shifting of said main pump.

8. In a hydraulic system a fluid operable motor, a reversible variable delivery main pump for supplying pressure fluid to said motor for actuating the same, double-acting servomotor means for controlling the delivery of said main pump, a reversible variable delivery pilot pump, doubleacting servomotor means for controlling the delivery thereof, a pair of conduits connecting said pilot pump oppositely. to said main servomotor means, a pair of conduits connecting said pilot pump oppositely to said pilot servomotor means,

external means adapted to be manually operated for overcoming said pilot servomotor means and additionally controlling the delivery of said pilot pump,. ielding means for allowing said pilot pump to be shifted towards neutral without changing the setting of said external means after said pilot pump has caused shifting of said main pump, means for normally urging said main pump to neutral, and means for allowing said last-named means to shift said main pump to neutral when said pilot pump has been shifted to neutral by said external means.

9. In a hydraulic system a fluid operable motor, a variable delivery main pump for supplying pressure fluid to said motor for actuating the same, servomotor means for controlling the delivery of said main pump, a one-way variable delivery pilot pump, and conduit means connecting the output of said pilot pump to said servomotor means, whereby said pilot pump is operative to actuate said servomotor means to control the delivery of said main pump.

- 10. In a hydraulic system a fluid operable motor, a variable delivery main pump for supplying pressure fluid to said motor for actuating the same, servomotor means for shifting said main pump to stroke, a one-way variable delivery pilot pump, servomotor means for shifting said pilot pump towards neutral, and conduit means for connecting the output of said pilot pump to both of said servomotor means.

11. In a hydraulic system a fluid operable motor, a variable delivery main pump for supplying pressure fluid to said motor for actuating the same, servomotor means for shifting said main pump to stroke, a one-way variable delivery pilot pump, means normally urging said pilot pump to stroke, servomotor means for shifting said pilot pump towards neutral, and conduit means for connecting the output of said pilot pump to both of said servomotor means.

12. A hydraulic system comprising a hydraulically operable plunger, a reversible variable delivery main pump to supply pressure fluid to said plunger for reciprocating the same, doubleacting servomotor means associated with said main pump to selectively move said main pump n one or the other direction, a reversible variable delivery pilot pump for supplying pressure fluid to said servomotor means, a pair of conduits connecting said pilot pump to said servomotor means, means operable in response to the of said plunger for preventing intercominunication between said conduits during a predetermined period of operation of said plunger, or establishing free communication between said conduits at the end of the retraction stroke of said plunger.

13. In a hydraulic system, a hydraulic motor, a variable delivery main pump for supplying pressure fluid to said motor to actuate the same, servomotor means associated with said main pump for controlling the delivery thereof, '9. variable delivery pilot pump adapted to supply pressure fluid to said servomotor means for actuating the latter, pressure responsive means for moving said pilot pump to a restricted delivery position in response to a predetermined pressure in said servomotor means, lever means operable to shift said pilot pump in one direction into full stroke position, and means interconnecting said lever means and said pilot pump and adapted to allow movement of said pilot pump from said full stroke position to a restricted stroke position without afiecting the position of said lever means.

14. In a hydraulic system, a hydraulic motor, a reversible variable delivery main pump for supplying pressure fluid to said motor to actuate the same, servomotor means associated with said main pump for controlling the delivery thereof, a variable delivery pilot pump adapted to supply pressure fluid to said servomotor means for actuating the latter, pressure responsive means for moving said pilot pump to a restricted delivery position in response to a predetermined pressure in said servomotor means, solenoid means operable to move said pilot pump in one direction into full stroke forward delivery position, means associated with said pilot pump for moving the same in the opposite direction into full stroke retraction position, and yielding means interconnecting said solenoid means and said pilot pump and adapted to allow movement of said pilot pump from full stroke forward delivery position to a restricted forward delivery position without aflecting the setting of said solenoid means.

15. A hydraulic system comprising a hydraulically reciprocable plunger, a reversible variable delivery main pump for supplying pressure fluid to said plunger to actuate the same, first servomotor means associated with said main pump and including two oppositely effective fluid chambers for controlling the delivery of said main pump, first yielding means urging said main pump to neutral or substantially no delivery position, a reversible variable delivery pilot pump operable selectively to supply pressure fluid to one or the other of said chambers, second yielding means continuously urging said pilot pump on stroke in one direction, actuating means for shifting said pilot pump on stroke in the opposite direction, against the thrust of said second yielding means, second servomotor means associated with said pilot pump and including a double-acting fluid operable piston for controlling the delivery of said pilot pump, said doubleacting piston being adapted in response to a pre-= determined pressure condition in said first servomotor means to move said pilot pump. toward neutral position, and means responsive to a predetermined point of travel of said plunger for hydraulically interconnecting said two chambers,

WARREN R. TUCKER. 

